Chemicals In Batteries
A battery is a device that converts chemical energy into electrical energy for use by electronic appliances. The chemical energy is stored in two or more electrochemical cells. The battery has both positive and negative electrodes that help facilitate the transfer of energy |
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Chemicals used in batteries
Different electronics require batteries of different chemical compositions to run on. For example, a dry cell comprises of a carbon rod put in a mixture of NH4Cl, ZnCl2 and MnO2. This is placed in a Zinc canister. The anode consists of oxidation of zinc to Zn2+. Cathode is reduction of NH4+ to NH3 and H2, both in their gaseous state. These gases are converted to water and zinc salts in the presence of other chemicals.
An alkaline battery uses zinc anode, similar to a dry cell battery. But it uses a steel canister instead of a zinc one. The chemical paste is a mixture of alkaline. The oxidizing element here is MnO2. Anode used here has Zn(s) + OH (-) and ZnO (s) + H2O (l) + 2 e-Cathode reactor is 2MnO2 + H2) (l) +2 e-. An alkaline battery does not cause production of gases. Zinc’s chemical conversion is different here because of the use of alkaline paste.
A mercury battery, often used in watches, is somewhat similar to alkaline battery in its composition. It uses mercury oxide in cathode and NaOH or KOH as the paste. The chemical reaction of a mercury battery is HgO (s) + H2O (l) + 2e- +2OH.
These three batteries are non-rechargeable. They are ‘dead’ once the electron transfer between the two electrodes is complete. However, they can be recycled.
To overcome this limitation, rechargeable batteries have been introduced. These are also referred to as ‘storage batteries’. An example is the lead storage battery that is commonly used in cars. As the name suggests, it uses porous lead as anode ad compressed lead oxide (PbO2) as cathode. The transfer of energy from anode to the source, from the source to cathode and then back, is reversible; thereby making it a chargeable battery. But the electrodes get decomposed and corroded over a period. Then it’s time for a new battery.
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The story of the battery begins in 1800 when it was invented by Italian physicist Count Alessandro Volta. The first battery was a pile of copper zinc discs. These were layered in between with cardboard disks that had coating of salt or acidic solution. 
